French President Nicolas Sarkozy has been overheard saying he "can't stand" Israeli Prime Minister Benjamin Netanyahu and calling him a liar in a chat with President Barack Obama.

The conversation was heard by reporters last week at the G20 summit in France, via headsets that were to be used for simultaneous translation of a news conference.

Mr Obama was not heard objecting to Sarkozy's characterisation of Mr Netanyahu. Through an interpreter, he was heard asking Mr Sarkozy to help persuade the Palestinians to stop their efforts to gain UN recognition of a Palestinian state.

Several French-speaking journalists overheard the comments but did not initially report them because Mr Sarkozy's office had asked them not to turn on the headsets until the press conference began, and the comments were deemed private under French media traditions.

But a French website that analyses media coverage of current affairs, Arret sur images, reported the fragments.

Mr Sarkozy's office would not comment on the remarks, or on France's relations with Israel. The White House and Mr Netanyahu's spokesman also said they had no comment.